Collector for neutral particles



A ril 28, 1964 w. A. KUHRT 3,130,542

COLLECTOR FOR NEUTRAL PARTICLES 7 Filed 001;. 26, 1962 EVM/Z;

United States Patent 3,130,542 COLLECTOR FGR NEUTRAL PARTICLES Wesley A. Kuhrt, Glastonbury, Conn, assignor to United Aircraft Corporation, East Hartford, Conn, a corporation of Delaware Filed Oct. 26, 1962, Ser. No. 233,274 8 Claims. (Cl. 6035.5)

This invention relates to ion propulsion devices. More particularly, this invention relates to the improvement of ion engine efliciency by collecting and recirculating the un-ionized particle discharge from an ion propulsion engine.

The discharge from an ion engine contains un-ionized or neutral particles which represent a waste of propellant and an impairment of the efliciency of the ion engine. The present invention uses a collector surrounding the exhaust beam of an ion engine to accumulate the neutral particles, and the neutral particles are then recirculated through the ion engine as part of the propellant supply to the engine. In this manner, the neutral particle discharge from the ion engine which would be otherwise represent a waste of propellant is recirculated for use, thereby increasing the efliciency of operation of the ion engine.

Accordingly, one feature of the present invention is a novel ion engine system having improved efficiency.

Another feature of the present invention is a novel ion engine system in which neutral particles discharged from the ion engine are collected and recirculated for use.

Still another feature of the present invention is a novel ion engine system in which a collector element surrounds the discharge beam from the ion engine and allows the passage of ionized particles while collecting most of the un-ionized particles.

Other features and advantages will be apparent from the specification and claims, and from the accompanying drawing which illustrates an embodiment of the invention.

The single figure in the drawing shows an ion engine with the neutral particle collector system.

Referring to the drawing, an ion engine is indicated generally at 2, and the ion engine is mounted in any convenient manner to a vehicle or load 4 to be propelled. The beam leaving the discharge end 6 of the ion engine is of approximately the same size as the opening of the discharge end, and the charged particles 8 in the beam travel along a path substantially parallel to the axis of the ion engine. However, Lin-ionized or neutral particles 10 also pass thorugh the discharge end of the ion engine, and these neutral particles leave the ion engine in random fashion, especially in the high vacuum condiiton associated with a space environment. The neutral particles 10 represent a waste of propellant and impair the efliciency of operation of the engine 2.

An annular collector element extends downstream of the discharge end of engine 2 and surrounds the dis charge beam from the engine. The collector 12 is shown in the shape of a truncated cone, but it will be understood that other surfaces, such as a hemisphere, could also be used. Collector 12 has a central opening 14 of approximately the same diameter as the opening of the discharge end 6 of the ion engine, and the charged particle beam passes through opening 14. Collector 12 is rotatably mounted on vehicle or housing 4 through suitable bearings 16. An inwardly directed flange 18 at the large end of collector 12 cooperates with the inner surface of the collector to form an annular manifold 20, and the entire collector is rotated through a motor 22 which drives a gear 24 which meshes with a ring gear 26 mounted on flange 18.

The curved end 28 of a conduit 30 is in communication with manifold 20. A rod 32 pivoted at 34 is connected at 36 to the curved end 28, and tension spring 38 normally pulls the left end of rod 32 upward to normally position end 28 in the dotted poistion at the periphery of manifold 2d, a flexible connection 40 in conduit 30 allowing for the movement of end 28. Conduit 30 has a pump 42 therein driven by a motor 44, and the discharge side of pump 42 is connected to fuel tank or propellant supply 46 from which propellant flows through heater 48 to the ion engine.

A solenoid plunger 50 is attached to the left side of rod 32, and both motor 44 and coil 52 are energized from battery 54. A pressure sensitive switch 56 in the circuit provides a series connection between motor 44 and coil 52; however, it will be apparent that a parallel connection could also be made if desired. Pressure switch 56 is normally opened so that motor 44 and solenoid 52 are normally de-energized.

In the operation of the present invention, propellant, such as cesium, is delivered from tank 46 to heater 48 where it is vaporized and then delivered to ion engine 2. The beam of charged particles discharged from engine 2 passes through opening 14 to provide propulsive thrust. Although some of the neutral particles will also pass through opening 14, most of the neutral particles impinge on the inner surface of collector 12 which is at a temperature cool enough to cause the neutral particles to condense to the liquid state. Of course, it will be apparent that a cooling system can be provided to cool collector 12 if necessary; however, in the outer space operational environment of ion engines collector 12 will be sutficiently cooled to condense the neutral particles in most circumstances. Collector 12 is continuously rotated, and the neutral particle condensate is centrifugally forced into manifold 26 where it accumulates. As the accumulation of neutral particle condensate builds up in conduit 20 the opened end of the curved portion 28 of conduit 30 (located in the dotted position) becomes immersed in the condensate, and the condensate enters conduit 3 3 to pressurize pressure switch 56. When the pressure on switch 56 reaches a predetermined level, the switch is actuated to close the electrical circuit and energize motor 44 and solenoid 52. The left end of rod 32 is then located counterclockwise and the curved end 28 of the conduit is immersed deeply into the condensate in manifold 20. At the same time, pump 42 begins to operate, and the accumulated condensate in manifold 20 is pumped out of manifold 20 and delivered to propellant tank 46 for reuse. As manifold 29 becomes drained of condensate, the pressure acting on switch 56 decreases, and switch 56 opens to break the circuit and de-energize motor 44 and coil 52 thereby terminating the action of pump 42 and returning the end 28 of the conduit to the dotted position. This sequence is repeated each time that a predetermined amount of condensate accumulates in manifold 20 through the rotating action of collector 12. As an alternative, switch 56 could be a timing mechanism so that the draining of manifold 20 would occur at predetermined time intervals rather than as a function of the build-up of condensate in the manifold.

It is to be understood that the invention is not limited to the specific embodiment herein illustrated and described but may be used in other ways without departure from its spirit as defined by the following claims.

I claim:

1. In combination with an ion acceleration device from which charged particles and neutral particles of propellant are discharged, a propellant storage tank, means for collecting neutral particles discharged from said ion acceleration device, and means for delivering said collected neutral particles to said propellant storage tank.

2. The combination as in claim 1 wherein the means for collecting neutral particles includes an annular member extending at least partly beyond the discharge end of said ion acceleration device and having a central opening substantially in alignment with the discharge end of said ion acceleration device.

3. The combination as in claim 2 wherein said annular member is rotatably mounted with respect to said ion acceleration device.

4. The combination as in claim 1 wherein said means for delivering said collected neutral particles includes means for sensing the accumulation of neutral particles in said collecting means, and means actuated by said sensing means for actuating pumping means to pump the accumulated neutral particles to said propellant storage tank.

5. In combination with a vehicle to be propelled, an ion propulsion device mounted on said vehicle, said ion propulsion device having a discharge end from which charged particles and neutral particles are discharged, an annular collecting element rotatably mounted on said vehicle for collecting neutral particles discharged from said ion propulsion device, said collecting element being in substantially axial alignment with said ion propulsion device and at least part of said collecting element extending beyond the discharged end of said ion propulsion device, said collecting element having an opening in axial alignment with the discharge end of said ion propulsion device, a propellant supply connected to said ion propulsion device, and means for delivering the neutral particles from said collecting element to said propellant supply.

6. The combination as in claim 5 wherein said collecting element decreases in diameter downstream of the discharge end of said ion propulsion device.

7. The combination as in claim 6 wherein said collecting element has a manifold, and wherein said delivering means includes a conduit communicating with said manifold and means for pumping the accumulation of neutral particles from said manifold to said propellant supply.

8. The combination as in claim 7 wherein said conduit is movable between a normally first position at the periphery of said manifold and a second position within said manifold, and including means for sensing the accumulation of neutral particles in said manifold and means actuated by said sensing means for actuating said pumping means and moving said conduit from said first position to said second position.

References Cited in the file of this patent UNITED STATES PATENTS 

5. IN COMBINATION WITH A VEHICLE TO BE PROPELLED, AN ION PROPULSION DEVICE MOUNTED ON SAID VEHICLE, SAID ION PROPULSION DEVICE HAVING A DISCHARGE END FROM WHICH CHARGED PARTICLES AND NEUTRAL PARTICLES ARE DISCHARGED, AN ANNULAR COLLECTING ELEMENT ROTATABLY MOUNTED ON SAID VEHICLE FOR COLLECTING NEUTRAL PARTICLES DISCHARGED FROM SAID ION PROPULSION DEVICE, SAID COLLECTING ELEMENT BEING IN SUBSTANTIALLY AXIAL ALIGNMENT WITH SAID ION PROPULSION DEVICE AND AT LEAST PART OF SAID COLLECTING ELEMENT EXTENDING BEYOND THE DISCHARGED END OF SAID ION PROPULSION DEVICE, SAID COLLECTING ELEMENT HAVING AN OPENING IN AXIAL ALIGNMENT WITH THE DISCHARGE END OF SAID ION PROPULSION DEVICE, A PROPELLANT SUPPLY CONNECTED TO SAID ION PROPULSION DEVICE, AND MEANS FOR DELIVERING THE NEUTRAL PARTICLES FROM SAID COLLECTING ELEMENT TO SAID PROPELLANT SUPPLY. 